Photogrammetic stereoscope



June 24, 1941. WTH 246,604

PHOTOGRAMMETI G STEREOS COPE Filed Dec. 31, 1938 INVENTOR Patented June 24, 1941 PHOTOGRAMMETIC STEREOSCOPE John Wesley Smith, Chestnut Hill, Pa., assignor to Philadelphia Air Transport Company, Norristown, Pa., a corporation of Pennsylvania Application December 31, 1938, Serial No. 248,657

4 Claims.

The present invention relates to stereoscopes and is especially directed to the provision of a novel and convenient instrument of this class intended primarily for examination and study of photogrammetics such as pairs of air mapping pictures and the like showing views of a subject taken from two different points, the stereoscope being adapted to blend or merge the two views in such a way as to make the subject appear in accurate three dimensional relief whereby elevations as well as horizontal distances may be observed and measured to scale or estimated from observation of such pictures through the medium of the instrument.

Stereoscopy is becoming more and more widely used in air mapping, aerial and geodetic surveys, topographic triangulation and other important and exact work, for example, the ascertainment of areas planted to difierent crops and other information required by governmental agencies and others in connection with present day agriculture control and promotion measures.

Stereoscopes heretofore used for such purposes have been of cumbersome and unwieldly nature and not always capable of convenient adaptation to suit varying conditions such as scale differences in two photogrammetic views of a given subject and inter-pupilary variation between different observers; it is therefore a principal object of my invention to provide an accurate and convenient folding stereoscope which can be set up and placed in operation or folded for transport or storage within a fraction of a minute and which when set up is readily adjustable to accommodate a Wide range of scale differences in the photogrammetic views being examined as well as inter-pupilary variation among different users.

Another object of the invention is to provide in a folding stereoscope of the character mentioned novel and effective means for controlling and adjusting the positions of the eyepiece mirrors or reflectors to thereby adapt the stereoscope for use with substantially all kinds of photogrammetics and enable it to fulfill substantially all conditions normally encountered in practice without impairing its foldability, lightness and convenience whereby its use in the field as well as its transport and storage are greatly facilitated.

It is a further object of the invention to provide a folding stereoscope of this character with the aid of which photogrammetic views may be examined without requiring special lighting facilities and while so positioned as to be readily accessible to the user if it be desired to sketch or mark directly upon them during their examination.

Other objects, purposes and advantages of the invention will hereinafter more fully appear or will be understood from the following description of a preferred embodiment thereof as shown in the accompanying drawing in which:

Fig. 1 is a rear perspective View of the stereoscope set up in position for use in photogrammetic examination of aerial maps or the like.

Fig. 2 is a rear elevation thereof partially broken away into vertical section.

Fig. 3 is a fragmentary bottom plan View of the eyepiece mirror adjusting mechanism and associated parts.

Fig. 4 is a similar View of the same with the eyepiece mirrors and their supports removed.

Fig, 5 is a perspective View of the stereoscope in folded condition.

Fig. 6 is a fragmentary rear elevation of a part of the stereoscope with one of the eyepiece mirrors positioned for folding.

In the several figures, like characters are used to designate the same parts.

Referring now more particularly to the drawing, the stereoscope shown comprises a pair of similar fairly shallow casings l, i. preferably formed of cast aluminum or other light and fairly rigid material, each casing having a substantially trapezoidal bottom and a peripheral rim. Bails 3 and 4 of heavy wire or the like are respectively associated with the casings and shaped to substantially conform to their sides, the ends of the bails being inturned and fitted into holes adjacent opposite corners of the latter so that the bails can be swung outwardly in parallelism with the respective casings and slipped into notches 5, 6 at the adjacent corners thereof to maintain the bails in substantial prolongation of the casings to serve as supports for the stereoscope when resting on a table T or the like as indicated in Figs. 1 and 2.

When these bails are sprung out of the notches in the casing corners and swung through about their inturned ends they snugly conform to the sides of the casings to permitthe latter to be folded into the smallest possible space as shown in Fig. 5.

0n the inner faces of the casing bottoms plane mirrors 1', 8 are suitably secured as by screws 9 and clips l0 extending along the edges of the mirrors and adjacent the side walls of the casings, while at the top edges of the latter are pivoted arms ll, l2, the opposite ends of which are hinged together on a rod M extending through suitable bosses l5 integral with the arms.

Removable tie rods l6, l! and [8 having their ends bent at right angles to their length are provided and operate as means for releasably holding the arms H and i2 and casings l and 2 in fixed relation at an angularity of 90 to each other when the stereoscope is set up as indicated in Fig. 2. The ends of the rods 16 and I! are thus bent in the same plane but in opposite directions while those of rod l8 are bent in the same direction, the rod ends being merely inserted in suitable holes in the respective parts when setting up the instrument and therefore capable of easy removal when the stereoscope is to be folded. The rod l8, in addition to holding the arms H and [2 in position, supports a head rest consisting of a plate 59 welded or otherwise secured to the rod and a sponge rubber or other resilient pad 29 carried by the plate and crimped thereto through the medium of its turned-in ends.

The arms H and [2 adjacent their rear edges have rectangular grooves 2| and 22 disposed in offset parallel relation transversely of the axis of the rod i4 and adapted to receive stems 23, 24 espectively supporting eyepiece mirrors 25, 255. The stems have rack teeth on their inner faces for engagement with pinion teeth of a sleeve 23 carried by the rod i4 adjacent the grooves 2 l, 22 and the sleeve, which is secured to the rod, has a circumferential groove 29 in its periphery adapted for reception of a pin fixed in the arm 12 to maintain the sleeve and hence the rod in the desired position longitudinally while allowing them to be freely rotated manually be means of the projecting milled end 230, of the sleeve whereby the stems 23 and 24 can be oppositely correspondingly moved in their grooves and consequently the mirrors 25 and 26 adjusted relatively to the casing or objective mirrors 1, 8.

The stems 23 and 26 are held in their grooves by leaf springs 3!, 32 respectively secured to the arms by screws 33, 34 whereby under normal conditions the rack teeth on the stems are kept in engagement with the teeth on the sleeve 28 to enable the aforesaid adjustment of the mirrors, although by moving the stems outwardly away from the sleeve against the tension of these springs the relative positions of the mirrors 25 and 26 may be easily changed by slipping the rack teeth of either or both stems in the desired direction past the teeth of the sleeve 23, the springs restoring the normal engagement of the racks with the sleeve when the stems are released.

The heads of the stems Z3 and 24 are substantially L-shaped and preferably square in section as indicated in Fig. 6, the head 35 of the stem 2 engaging the rear face of the mirror 25 and being yieldingly clamped thereto by a spring 35 secured to the back face of the mirror frame. Ihus the mirror can be moved about the axis of the stem head but is in equilibrium in positions such that its general plane lies in parallelism with the adjacent arm or normal thereto, an angular clip 33 engaging one end of the head servin to prevent the mirror from being moved longitudinally of the latter after the mechanism has been initially assembled. A substantially similar arrangement of like parts maintains the mirror 25 in adjustable assembled relation with its stem 23.

As will be apparent from the dot and dash lines in Fig. 2, when the stereoscope is in use the mirrors '25 and 26 are'respecti'vely maintained in substantial parallelism with the casing mirrors 1 and 8 and the latter are disposed in planes substantially normal to each other at approximately 45 to the plane of table T, so that when one eye of the user is in the line of sight of each of the eyepiece mirrors 25, 26 his field of view is formed by the spaced maps M-M or other photogrammetic views disposed on the table or other support on which the stereoscope is positioned. The user while viewing the eyepiece mirrors in this manner may rest his head on the head rest 20 and thereby attain maximum stability during his work and can then easily adjust the relative spacing of the mirrors 25, 26 from their respectively adjacent casing mirrors 3 and 8 by merely rotating the sleeve end 28a. Thus moving the latter in a clockwise direction in Fig. 2 causes the mirror 25 to move closer to the mirror 1 and the mirror 26 simultaneously to move farther away from the mirror 8 and counter-clockwise rotation of the sleeve reverses these movements. It is consequently an extremely simple matter to adjust these mirrors to compensate for a difference in scale between the photogrammetic views MM so as to permit them to be viewed as component parts of a single three dimensional representation of their subject.

When adjustment of the stereoscope is required because of difference in the inter-pupilary distance of successive users, one of the stems is moved against its retaining spring to permit its rack teeth to clear the teeth on sleeve 28 and is then slid to the required extent past these teeth and released so as to restore the normal mutual engagement of the teeth; a wide range of interpupilary variation can thus readily be compensated for and the eye strain resulting from improperly spaced eyepieces thereby avoided, adjustment for scale differences in the manner hitherto explained of course being effected after the adjustment for inter-pupilary variation has been made.

The wide spacing of the mirrors 1, 8, permits accurate study of pictures or the like taken from widely spaced points and thus brings out the three dimensional relief with great clarity and precision, enabling relief to be observed in pictures with far greater accuracy than with the naked eye or even with stereoscopic binoculars or the like.

Furthermore the bails 3, 4, when engaged in the notches 5, 6, with their ends entered in the holes provided for them in the casings support the remainder of the mechanism a considerable distance above the table T to permit sketching or other work directly upon the views M--M' while they are being subjected to stereoscopic examination while the bails themselves rest on the table at widely separated points so that ample space is afforded for relatively large views between their lower ends whereby large areas may be examined without moving either the views or any part of the stereoscope.

When the stereoscope is to be folded for transport or storage, the rods it, ill and I8 are removed from the holes in which their ends are respectively engaged thereby permitting the casings I and 2 and arms ii and [2 to be moved relatively to each other about their several hinged connections. Before they are brought together, however, in order to take advantage of the extreme compactness my stereoscope affords, it is desirable to turn the eyepiece mirrors 25 and 26 through an arc of on their supporting stems so that as indicated in Fig. 6 they lie in parallelism with the latter instead of in normal relation thereto. They then do not interfere with the mutual engagement of the casing rims and the latter can thus be brought together with the result that the arms II and I2 and mechanism carried thereby are entirely enclosed within a substantially dust-proof housing formed by the now juxtaposed casings, the front end of the shaft I4 being preferably made long enough to project beyond the arms II and I2 for reception in notches 40, 4| in the casing rims to thereby steady the arms when folded within the housing and prevent them from being inadvertently brought against either of the mirrors I, 8. Of course, the bails 3 and 4 are reversed so as to lie snugly adjacent the casings when the stereoscope is folded and the latter then appears as in Fig. 5, in which condition it is extremely compact and safely arranged for transport or storage since all the fragile or delicate parts including the mirrors, the adjusting mechanism therefor and the connecting arms, are fully enclosed and protected. If desired, a suitable metal clip (not shown) or other means may be employed to hold the bails and/or the casing members together when the stereoscope is folded and the latter may then safely be carried in a pocket of sufficient size or otherwise conveniently transported although capable of being set up again for use within a fraction of a minute, only a little, if any, longer than the time required for folding it.

The convenience with which the stereoscope can be folded and/or unfolded and set up for use renders it invaluable for field work by military forces or others requiring great speed and flexibility of use as well as accuracy and dependability in instruments of this general class.

While I have herein described a specific embodiment of the invention with considerable particularity, it will be understood I do not desire or intend to limit or confine myself thereto in any way as changes and modifications in the form, construction, and arrangement of the several parts, in their mode of assembly and in the details of their operation will readily occur to those skilled in the art and may be made if desired without departing from the spiritand scope of the invention as defined in the appended claims.

Having thus described my invention, I claim and desire to protect by Letters Patent of the United States:

1. A folding stereoscope comprising a pair of casings each having a substantially plane bottom and a peripheral rim adapted to be brought into engagement with the rim of the other casing, reflectors carried by the bottoms of the casings, arms respectively hinged to each casing and to each other, means for releasably maintaining the arms and casings in fixed angular relation, a reflector carried by each arm adapted to be positioned in substantial parallelism with and movable toward and away from the reflector in the adjacent casing and means carried by the arms for simultaneously moving the arm reflectors in opposite directions relatively to the respectively adjacent casing reflectors comprising angularly disposed racks respectively supporting the arm reflectors from the arms and including within their angle the axis of the arm hinge and a pinion coaxial with said hinge engaging the racks and operable upon its rotation to move the racks longitudinally in opposite directions with respect to said axis.

2. A folding stereoscope comprising a pair of casings each having a substantially plane bottom and a peripheral rim adapted to be brought into engagement with the rim of the other casing, reflectors carried by the bottoms of the casings, arms respectively hinged to each casing, means for releasably maintaining the arms and casings in fixed angular relation, alined lugs carried by each arm remote from the casings, a rotatable shaft extending through all of said lugs and provided with a pinion, a rack carried by each arm adapted to engage said pinion and a reflector supported on each rack and adjustable in opposite directions relatively to the adjacent casing reflector by rotation of said shaft,

3. In a foldable stereoscope comprising a pair of substantially similar oppositely disposed casings, a reflector in each casing, a pair of arms respectively hinged to the casings and to each other, releasable means for maintaining the arms and casings in fixed angular relation, a rack carried by and movable in a plane'paralleling each arm, reflectors respectively supported from the racks and movable therewith as well as relatively thereto about axes normal to the paths of movement of the racks, and a pinion engaging the racks for moving them and the reflectors simultaneously in opposite directions relatively to the casing reflectors.

4. In a foldable stereoscope of the character described, a pair of reflectors adapted to be maintained in fixed angular relationship respectively at an included angle of substantially 45 to a supporting surface to thereby project along sub stantially parallel paths and in opposite directionslight rays received from objects disposed on said surface, a pair of eyepiece mirrors disposed between said reflectors respectively in substantial parallelism therewith and adapted to reflect said rays along parallel paths in substan tially the same direction normal to said surface and at less distance from each other than said objects, and means interconnecting the eyepiece mirrors with the reflectors comprising casings for the reflectors, arms pivoted to the casings and to each other, racks supported by the arms for movement respectively in planes normal to the planes of the adjacent reflectors, means supporting the eyepiece mirrors from the racks and a pinion engaging said racks operable to move them simultaneously in opposite directions relatively to the adjacent reflectors.

JOHN WESLEY SMITH. 

